CONTROLLING POLYMER-SURFACE INTERACTIONS WITH RANDOM COPOLYMER BRUSHES

A simple technique for precisely controlling the interfacial energies and wetting behavior of polymers in contact with solid surfaces is des cribed, End-functionalized statistical random copolymers of styrene an d methylmethacrylate were synthesized, with the styrene fraction f var ying from 0 to 1, and were end-grafted onto silicon substrates to crea te random copolymer brushes about 5 nanometers thick, For f < 0.7, pol ystyrene (PS) films (20 nanometers thick) rapidly dewet from the brush es when heated well above the glass transition temperature. The contac t angle of the resulting polymer droplets increased monotonically with decreasing f. Similar behavior was observed for poly(methylmethacryla te) (PMMA) films but with an opposite dependence on f. The interfacial energies of the random copolymer brushes with PS and PMMA were equal when f was about 0.6. Thus, precise control of the relative surface af finities of PS and PMMA was possible, demonstrating a way to manipulat e polymer-surface interactions.